Photoresist compositions comprising blends of photoacid generators

ABSTRACT

The invention provides new photoresist compositions that contain a resin binder and a blend of photoacid generators. Photoacid generator blends of the invention produce photoacids that differ in acid strength and/or size.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to new photoresist compositions that contain ablend of photoacid generator compounds. Compositions of the inventionare highly useful as deep U.V. photoresists.

2. Background

Photoresists are photosensitive films for transfer of images to asubstrate. They form negative or positive images. After coating aphotoresist on a substrate, the coating is exposed through a patternedphotomask to a source of activating energy such as ultraviolet light toform a latent image in the photoresist coating. The photomask has areasopaque and transparent to activating radiation that define an imagedesired to be transferred to the underlying substrate. A relief image isprovided by development of the latent image pattern in the resistcoating. The use of photoresists is generally described, for example, byDeforest, Photoresist Materials and Processes, McGraw Hill Book Company,New York (1975), and by Moreau, Semiconductor Lithography, Principals,Practices and Materials, Plenum Press, New York (1988).

Known photoresists can provide features having resolution and sizesufficient for many existing commercial applications. However for manyother applications, the need exists for new photoresists that canprovide highly resolved images of submicron dimension.

Various attempts have been made to alter the make-up of photoresistcompositions to improve performance of functional properties. Amongother things, a variety of photoactive compounds have been reported foruse in photoresist compositions. See, e.g., U.S. Pat. No. 4,450,360 andEuropean Application 615163.

Relatively recently interest has increased in photoresists that can bephotoimaged with deep U.V. radiation. Such photoresists offer thepotential of forming images of smaller features than may be possible atlonger wavelength exposure. As is recognized by those in the art, “deepU.V. radiation” refers to exposure radiation having a wavelength in therange of about 350 nm or less, more typically in the range of about 300nm or less. While a number of deep U.V. resists have been reported, theneed clearly exists for new deep U.V. resists that can provide highlyresolved fine line images as well as acceptable photospeed and otherlithographic properties. Particular interest exists in resists that canbe imaged with sub-250 nm wavelengths such as KrF radiation (ca. 248 nm)or sub-200 nm wavelengths such as ArF radiation (193 nm).

SUMMARY OF THE INVENTION

We have now discovered novel blends or mixtures of photoacid generatorscompounds (“PAGs”) that can formulated in photoresist compositions toprovide excellent lithographic properties, particularlychemically-amplified positive-acting resists. Preferred PAG blends canbe photoactivated upon exposure to deep U.V. radiation, particularly 248nm.

In a first aspect of the invention, PAG blends are provided thatphotogenerate acids of differing strengths. More particularly, preferredPAG blends comprise at least one PAG that generates a strong acid uponphotoactivation, and at least one PAG that generates a comparativelyweak acid upon photoactivation. Typically, the “strong” and “weak”photogenerated acids of the blend differ in pKa values (determined byTaft parameter calculation as discussed in detail below) by at leastabout 1 or 1.5, more typically a pKa difference of at least about 2 ormore. A typical “strong” photogenerated acid of a blend of the inventionhas a pKa (Taft parameter calculation) of about −1 or less, moretypically a pKa of about −2, −3 or lower. A typical “weak”photogenerated acid of a blend of the invention has a pKa (Taftparameter calculation) of about −2, −1, 0 or higher.

For instance, illustrative preferred “strong” photogenerated acidsinclude perfluorinated alkylsulfonic acids e.g. perfluorooctanesulfonicacid, perfluorohexanesulfonic acid, perfluorobutanesulfonic acid,perfluoro(4-ethyl)cyclohexanesulfonic acid, trifluoromethanesulfonicacid and the like. Additional suitable “strong” photogenerated acidsinclude aromatic sulfonic acids that are substituted with electronwithdrawing groups such as fluoro, nitro, cyano and trifluoromethyl.Suitable “strong” photogenerated acids for use in the blends of theinvention may include pentafluorobenzenesulfonic acid,2-trifluoromethylbenzenesulfonic acid, 3-trifluoromethylbenzenesulfonicacid, 4-trifluoromethylbenzenesulfonic acid, andbis(trifluoromethyl)benzenesulfonic acid, particularly3,5-bis(trifluoromethyl) benzenesulfonic acid.

Preferred “weak” photogenerated acids include e.g. alkylsulfonic acidsthat are not substituted with electron withdrawing groups such asfluoro, or have minimal electron withdrawing group substitution, e.g.only one or two electron withdrawing substituents. Cycloalkylsulfonicacids are particularly suitable “weak” acids, such ascyclohexanesulfonic acid, adamantanesulfonic acid, camphor sulfonic acidand the like. PAGs that may be employed to provide such acids includee.g. onium salts such as iodonium salts, sulfonium salts and the like;imidosulfonates;

sulfonate esters; and non-ionic halogenated compounds that generate ahalo-acid (e.g.

HBr) upon photoactivation.

In a further aspect, the invention provides PAG blends that generateacids of differing size upon photoactivation. More specifically, in thisaspect of the invention, preferred PAG blends comprise at least one PAGthat generates a “large” acid upon photoactivation, and at least one PAGthat a comparatively “small” acid upon photoactivation. Typically, the“large” and “small” photogenerated acids of the blend differ in size byat least about 25 or 30 cubic angstroms (i.e. Å³), more typically by atleast about 40 or 50 cubic angstroms (i.e. Å³). A typical “large”photogenerated acid of a blend of the invention has a volume of at leastabout 155 or 160 Å³), more preferably a volume of at least about 170,180 or 190 Å³. A typical “small” photogenerated acid of a blend of theinvention has a volume of about less than 155 or 150 Å³, more preferablya volume of about 130 or 140 Å³ or less. Sizes of photogenerated acidsmay be readily determined by standard computer-based analyses, as arewell-known and further discussed below.

PAG blends also are provided that combine both aspects of the invention,where the blend comprises PAGs that generate acids that differ both inacid strength and size. For example, PAG blends are provided thatcomprise at least one PAG that generates upon photoactivation a strongacid that is large (or small), and at least one PAG that generates uponphotoactivation a weak acid that is small (or large if the strong acidis small).

However, in at least some aspects of the invention, it is preferred thattwo PAGs of a blend differ only in either size or strength of thephotogenerated acid. Thus, e.g., in this aspect of the invention, if theblend members generate photoacids that differ in size as discussedabove, then those photogenerated acid have similar acid strengths, e.g.a pKa (Taft parmater calculation) difference of 0.5 or less. Similarly,in this aspect of the invention, if the blend members generatephotoacids that differ in strength as discussed above, then thosephotogenerated acid have similar size, e.g. less than about 25 or 20 Å³difference in size.

Without being bound by theory, it is believed that larger photogeneratedacids will diffuse more slowly (relative to a small acid) through aphotoresist layer after exposure and prior to development. Suchdiffusion, particularly into unexposed resist layer areas, can limitresolution of the developed image. It is also believed that a strongphotogenerated acid can provide enhanced photospeed (relative to a weakacid).

It has been found that selective blending of members of a PAG mixture ofthe invention can provide the optimal balance of properties selected fora particular resist containing the PAG blend.

Photoresist compositions are also provided that comprise a PAG blend ofthe invention. PAG blends of the invention can be used in a variety ofresist systems. In particular, PAG blends of the invention arepreferably formulated in chemically-amplified positive-acting resists,where the resist contains a polymer with photoacid-labile groups,particularly pendant acid-labile groups such as can be provided bycondensation of alkyl acrylate monomers, e.g. an alkyl acrylate-phenolcopolymer, or a polymer that contains alkyl acrylate repeat units andthat is essentially or completely free of phenyl or other aromaticunits. Unless otherwise indicated, the term acrylate as used hereinrefers to vinyl esters in general, including substituted compounds suchas methacrylate and the like.

It has been that photoresist compositions that contain PAG blends of theinvention can impart significantly improved lithographic properties tothe resist. See, for instance, the comparative results set forth inExamples 2, 3 and 4 which follow. Among other things, it has been foundthat resists of the invention can provide highly resolved resist reliefimages on substrates recognized to compromise resolution, such as boronphosphorus silicate glass. See the results set forth in Example 4 whichfollows.

The invention also provide methods for forming relief images of thephotoresists of the invention, including methods for forming highlyresolved patterned photoresist images (e.g. a patterned line havingessentially vertical sidewalls) of submicron and even sub-half microndimensions.

The present invention further provides articles of manufacturecomprising substrates such as a microelectronic wafer or a flat paneldisplay substrate having coated thereon the photoresists and reliefimages of the invention. Other aspects of the invention are disclosedinfra.

References herein to pKa values of photoacids designate valuesdetermined by Taft parameter analysis, as such analysis is known in thisfield and described in J. Cameron et al., “Structural Effects ofPhotoacid Generators on Deep UV Resist Performance,” Society of PlasticEngineers, Inc. Proceedings., “Photopolymers, Principles, Processes andMateials, 11^(th) International Conference, pp. 120-139 (1997); and J.P. Gutthrie, Can. J Chem., 56:2342-2354 (1978). References herein tosizes of photoacids designate volumetric size as determined by standardcomputer modeling, which provides optimized chemical bond lengths andangles. A preferred computer program for determining photoacid size isAlchemy 2000, available from Tripos. For a further discussion ofcomputer-based determination of photoacid size, see T. Omote et al.,Polymers for Advanced Technologies, “Photoreactive Fluorinated PolyimideProtected by a Tetrahydropyranyl Group Based on Photo-inducedAcidolysis”, volume 4, pp. 277-287.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, in a first aspect PAG blends are provided thatphotogenerate acids of differing strengths e.g. as assessed by pKavalues. In a further aspect, PAG blends are provided that generate uponphotoactivation acids of differing size.

A variety of PAGs can be employed in the PAG blends and photoresistcompositions of the invention.

Onium salts are generally preferred PAGs for use in accordance with theinvention. Examples of suitable onium salts include for example,halonium salts, quaternary ammonium, phosplionium and arsonium salts,aromatic sulfonium salts and sulfoxonium salts or selenium salts. Oniumsalts have been described in the literature such as in U.S. Pat. Nos.4,442,197: 4,603,101; and 4,624,912.

Generally preferred onium salts include iodonium salt photoacid(generators, such as those compounds disclosed in published Europeanapplication 0 708 368 A1. Such salts include those represented by thefollowing formula:

where Ar¹ and Ar² each independently represents a substituted orunsubstituted aryl group. A preferred example of the aryl group includesa C₆₋₁₄ monocyclic or a condensed ring aryl group. Preferred examples ofthe substituent on the aryl group include an alkyl group, a haloalkylgroup, a cycloalkyl group, an aryl group, an alkoxy (group, a nitrogroup, a carboxyl group, an alkoxycarbonyl group, a hydroxyl group,mercapto group, and a halogen atom. Suitable anion substituents Rinclude e.g. R is adamantane, alkyl (e.g. C₁₋₁₂) alkyl) andperfluoroalkyl such as perfluoro (C₁₋₁₂alkyl), particularly perfluorocounter anions of perfluorooctanesulfonate, perfluorononanesulfonate andthe like.

Two particularly suitable iodonium PAGs are the following PAGS 1 and 2:

Such compounds can be prepared as disclosed in European PatentApplication 96118111.2 (publication number 0783136), which details thesynthesis of above PAG 1.

Also suitable are the above two iodonium compounds complexed with anionsother than the above-depicted camphor sulfonate groups. In particular,preferred anions include those of the formula RSO₃ ⁻ where R isadamantane, alkyl (e.g. C₁₋₁₂ alkyl) and perfluoroalkyl such asperfluoro (C₁₋₁₂alkyl), particularly perfluoro counter anions ofperfluorooctanesulfonate, perfluorononanesulfonate and the like.

Sulfonium salts are particularly suitable photoacid generators for PAGblends and resists of the invention, such as compounds of the followingformula:

wherein R³, R⁴ and R⁵ each independently represents a substituted orunsubstituted alkyl group or aryl group. With regard to each of theabove formulae, preferred examples of the substituted or unsubstitutedalkyl group and aryl group include a C₆₋₁₄ aryl group, a C₁₋₅ alkylgroup, and substituted derivatives thereof. Preferred examples of thesubstituent on the alkyl group include a C₁₋₈ alkoxy group, a C₁₋₈ alkylgroup, nitro group, carboxyl group, hydroxyl group, and a halogen atom.Preferred examples of the substituent on the aryl group include a C₁₋₈alkoxy group, carboxyl group, an alkoxycarbonyl group, a C₁₋₈ haloalkylgroup, a C₅₋₈ cycloalkyl group and a C₁₋₈ alkylthio group. Two of R³, R⁴and R⁵ may be connected to each other via its single bond or asubstituent. R of the above sulfonium formulae may be the same asdefined above for the iodonium PAGs 1 and 2, i.e. adamantane, alkyl(e.g. C₁₋₁₂ alkyl) and perfluoroalkyl such as perfluoro (C₁₋₁₂alkyl),particularly perfluoro counter anions of perfluorooctanesulfonate,perfluorononanesulfonate and the like.

Additional preferred photoacid generators for use in the blends andresists of the invention include imidosulfonates such as compounds ofthe following formula:

wherein each R¹ and R¹′ are each independently hydrogen or C₁₋₁₂ alkyl,more preferably hydrogen or methyl; and R is alkyl (e.g. C₁₋₁₂ alkyl),camphor, adamantane and other cycloalkyl typically having from 5 toabout 12 ring members, and perfluoroalkyl such as perfluoro(C₁₋₁₂alkyl),particularly perfluorinated groups such as perfluorooctanesulfonate,perfluorobutanesulfonate and the like. R of that formula may be the sameas defined above for the iodonium and sulfonium PAGs. A specificallypreferred photoacid generator of this class is N-[(perfluorooctanesulfonyl)oxy]-5-norbornene-2,3-dicarboximide.

N-sulfonyloxyimide photoacid generators also are suitable for use in PAGblends and compositions of the invention, including thoseN-sulfonyloxyimides disclosed in International application WO94/10608,such as compounds of the following formula:

where the carbon atoms form a two carbon structure having a single,double or aromatic bond, or, alternatively, wherein they form a threecarbon structure, that is, where the ring is instead a five member orsix member ring; R is —C_(n)H_(2n+1) where n=1 to 8, —C_(n)F_(2n+1)where n=1 to 8, a camphor substituent, -2(9,10-diethoxyanthracene),—(CH₂)_(n)—Z or —(CF₂)_(n)Z where n=1 to 4 and where Z is H, C₁₋₆ alkyl,a camphor substituent, -2-(9,10-diethoxyanthracene, or aryl such asphenyl; X and Y (1) form a cyclic or polycyclic ring which may containone or more hetero atoms, or (2) form a fused aromatic ring, or (3) maybe independently hydrogen, alkyl or aryl, or (4) may be attached toanother sulfonyloxyimide containing residue, or (5) may be attached to apolymer chain or backbone, or alternatively, form

where R₁ is selected from the group consisting of H, acetyl, acetamido,alkyl having 1 to 4 carbons where m=1 to 3, NO₂ where m=1 to 2, F wherem=1 to 5, Cl where m=1 to 2, CF₃ where m=1 to 2, and OCH₃ where m=1 to2, and where m may otherwise be from 1 to 5, and combinations thereof,and where X and Y (1) form a cyclic or polycyclic ring which may containone or more hetero atoms, (2) form a fused aromatic ring, (3) may beindependently H, alkyl or aryl, (4) may be attached to anothersulfonyloxyimide containing residue, or (5) may be attached to apolymeric chain or backbone.

In certain embodiments of the invention, such N-sulfonyloxyimides areexcluded from PAG blends and resists of the invention, or at least suchN-sulfonyloxyimides are excluded from use in combination with asulfonium salt PAG, particularly a triphenyl sulfonium salt, or incombination with an iodonium salt PAG, particularly a diphenyl iodoniumsalt PAG. In certain embodiments, excluded from PAG blends and resistsof the invention will be mixtures of diphenyl-iodonium triflate,di-(t-butylphenyl)iodonium triflate, or phthalimide triflate.

Another class of photoacid generators suitable for use in the blends andresists of the invention include diazosulfonyl compounds such as thosedisclosed in U.S. Pat. No. 5,558,976. Representative examples of thesephotoacid generators include:

where R suitably is phenyl optionally substituted by halogen, C₁₋₈alkyl, C₁₋₈ alkoxy, or C₁₋₈ haloalkyl; C₁₋₈ alkyl; C₁₋₈ alkoxy; or C₁₋₈haloalkyl; R⁷ may be the same (e.g. symmetrical compound where Z issulfonyl) or different than R and in addition to the groups specifiedfor R, R⁷ may be a straight-chain, branched or cyclic alkyl group havingfrom 1 to 10 carbon atoms and Z is a sulfonyl group or a carbonyl group:

where R is as defined above; and

where R²² is hydrogen, hydroxyl or a group represented by the formulaRSO₂O— where R is as defined above, and R²³ is a straight or branchedalkyl group having from 1 to 5 carbon atoms or a group represented bythe formula:

where R²⁴ and R³⁰ are independently a hydrogen atom, a halogen atom, astraight chain or branched alkyl group having 1-5 carbon atoms, astraight chain or branched alkoxy group having 1-5 carbon atoms, or agroup of the formula:

where each R²⁵ is independently a straight chain or branched alkyl grouphaving 1-4 carbon atoms, a phenyl group, a substituted phenyl group oran aralkyl group; and R²⁶ is a hydrogen atom, hydroxy, a halogen atom ora straight-chain, branched or cyclic alkyl group having 1-6 carbonatoms, or alkoxy suitably having 1-6 carbons.

Nitrobenzyl-based photoacid generators may also be employed as a PAGcomponents of the blends and resists of the invention, including thosedisclosed in EPO published application No. EP 0 717 319 A1. Suitablenitrobenzyl-based compounds include those of the following formula:

where each R₁, R₂ and R₃ are individually selected from the groupconsisting of hydrogen and lower alkyl group having from 1-4 carbonatoms; and R₄ and R₅ are individually selected from the group consistingof CF₃ and NO₂ and R is optionally substituted carbocyclic aryl,particularly optionally substituted phenyl such as phenyl where the 2,3, and 4 position substituents are selected from hydrogen and C₁₋₄ alkyland where the 5 and 6 ring positions are selected from CF₃, NO₂ andSO3R′ where R′ of optionally substituted C₁₋₁₂ alkyl or aryl such asphenyl where such optional substituents may be C₁₋₄ alkyl, C₁₋₄ alkoxy,NO₂ or CF₃.

Disulfone derivatives are also suitable non-ionic photoacid generatorsfor use in accordance with the invention. Suitable compounds aredisclosed e.g. in published European application 0 708 368 A1. Suchmaterials may be represented by the following formula:

R—SO₂—SO₂—R′

wherein R and R′ may each be the same or different and may each be thesame as defined above for R, or R may be Ar³ where each Ar independentlyrepresents a substituted or unsubstituted aryl group. A preferredexample of the aryl group includes a C₆₋₁₄ monocyclic or condensed-ringaryl group. Preferred examples of the substituent on the aryl groupinclude an alkyl group, a haloalkyl group, a cycloalkyl group, an arylgroup, an alkoxy group, nitro group, carboxyl group, an alkoxycarbonylgroup, hydroxyl group, mercapto group, and halogen.

Halogenated non-ionic, photoacid generating compounds are also suitablefor use in blends and resists of the invention and include, for example,1,1-bis[p-chlorophenyl]-2,2,2-trichloroethane (DDT);1,1-bis[p-methoxyphenyl]-2,2,2-trichloroethane;1,2,5,6,9,10-hexabromocyclodecane; 1,10-dibromodecane;1,1-bis[p-chlorophenyl]-2,2-dichloroethane;4,4-dichloro-2-(trichloromethyl) benzhydrol (Kelthane);hexachlorodimethyl sulfone; 2-chloro-6-(trichloromethyl) pyridine;o,o-diethyl-o-(3,5,6-trichloro-2-pyridyl)phosphorothionate;1,2,3,4,5,6-hexachlorocyclohexane;N(1,1-bis[p-chlorophenyl]-2,2,2-trichloroethyl)acetamide;tris[2,3-dibromopropyl]isocyanurate;2,2-bis[p-chlorophenyl]-1,1-dichloroethylene;tris[trichloromethyl]s-triazine; and their isomers, analogs, homologs,and residual compounds. Suitable photoacid generators are also disclosedin European Patent Application Nos. 0164248 and 0232972. Acid generatorsthat are particularly preferred for deep U.V. exposure include1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT);1,1-bis(p-methoxyphenol)-2,2,2-trichloroethane;1,1-bis(chlorophenyl)-2,2,2 trichloroethanol;tris(1,2,3-methanesulfonyl)benzene; and tris(trichloromethyl)triazine.

PAG blends of the invention may contain more than two different PAGs,e.g. where multiple PAGs of a single class or type are present in aresist formulation. However, it is often preferred that a PAG blendconsists of no more than two distinct photoacid generators.

Some specifically preferred photoacids of PAG blends and resists of theinvention are shown immediately with pKa values (Taft parametercalculation) and/or volumetric size values (Å³) listed immediately belowthe acid.

CF₃SO₃H CF₃(CF₂)₃SO₃H CF₃(CF₂)₇SO₃H CF₃CF₂SO₃H pK_(a) = −5.21 pK_(a) =−5.00 pK_(a) = −4.71 108 A³ 79 A³ 154 A³ 244 A³ CH₃SO₃H CH₃(CH₂)₃SO₃HCH₃(CH₂)₇SO₃H CF₃(CF₂)₅SO₃H pK_(a) = −1.89 pK_(a) = −1.68 pK_(a) = −1.41208 A³ 68 A³

pK_(a) = −1.77 pK_(a) = −1.69 pK_(a) = −1.54 193 A³ 143 A³ 185 A³

pK_(a) = −2.70 pK_(a) = −2.73 pK_(a) = −2.66 140 A³ 137 A³

151 A³ pK_(a) = −3.21 pK_(a) = −3.27

pK_(a) = −2.87 pK_(a) = −2.58 pK_(a) = −3.31

As discussed above, a PAG blend of the invention is preferably used inpositive-acting chemically amplified resist compositions. Suchcompositions comprise a dissolution inhibitor component, e.g. a resinwith photoacid labile moieties.

The dissolution inhibitor component may contain any of a variety of acidlabile groups, such as acid sensitive esters, carbonates, acetals,ketals and the like, which suitably may be pendant from a polymerbackbone. Acid-labile groups that are integral to the polymer backbonealso may be employed. Preferred deblocking resin binders have also beendisclosed in European Patent Published Application EP0813113A1, EuropeanPatent Application 97115532 (corresponding to U.S. Pat. No. 5,861,231),and U.S. Pat. No. 5,258,257 to Sinta et al. Suitable deblocking resinsand use of same in chemically amplified photoresists also have beendescribed in U.S. Pat. Nos. 4,968,581; 4,883,740; 4,810,613; 4,491,628and 5,492,793.

Preferred deblocking resins for use in the resists of the inventioninclude polymers that contain both phenolic and non-phenolic units. Forexample, one preferred group of such polymers has acid labile groupssubstantially, essentially or completely only on non-phenolic units ofthe polymer. One preferred polymer binder has repeating units x and y ofthe following formula:

wherein the hydroxyl group be present at either the ortho, meta or parapositions throughout the polymer, and R′ is substituted or unsubstitutedalkyl having 1 to about 18 carbon atoms, more typically 1 to about 6 to8 carbon atoms. Tert-butyl is a generally preferred R′ group. An R′group may be optionally substituted by e.g. one or more halogen(particularly F, Cl or Br), C₁₋₈ alkoxy, C₂₋₈ alkenyl, etc. The depictedphenolic units of the polymer also may be optionally substituted by suchgroups. The units x and y may be regularly alternating in the polymer,or may be randomly interspersed through the polymer. Such copolymers canbe readily formed. For example, for resins of the above formula, vinylphenols and a substituted or unsubstituted alkyl acrylate such ast-butylacrylate and the like may be condensed under free radicalconditions as known in the art. The substituted ester moiety, i.e.R′—O—C(═O)—, of the acrylate units serves as the acid labile groups ofthe resin and will undergo photoacid induced cleavage upon exposure of acoating layer of a photoresist containing the resin. Preferably thecopolymer will have a Mw of from about 3,000 to about 50,000, morePreferably about 10,000 to about 30,000 with a molecular weightdistribution of about 3 or less, more preferably a molecular weightdistribution of about 2 or less. Such copolymers also may be prepared bysuch free radical Polymerization or other known procedures and suitablywill have a Mw of from about 3,000 to about 50,000, and a molecularweight distribution of about 3 or less, more preferably a molecularweight distribution of about 2 or less.

Additional preferred deblocking resins have acid labile groups on bothphenolic and non-phenolic units of the polymer. One preferred polymerbinder has repeating units a, b and c of the following formula:

wherein R′ group is a photoacid labile group as defined above for theother preferred polymer; X is another repeat unit which may or may notcontain a photoacid labile group; and each Y is independently hydrogenor C₁₋₆ alkyl, preferably hydrogen or methyl. The values a, b and cdesignate the molar amount of the polymer units. Those polymer units maybe regularly alternating in the polymer, or may be randomly interspersedthrough the polymer. Suitable X groups may be aliphatic or aromaticgroups such as phenyl, cyclohexyl, adamantyl, isobornylacrylate,methacrylate, isobornylmethacrylate, and the like. Such polymers may beformed in the same manner as described for the polymer above, andwherein the formed copolymer is reacted to provide the phenolic acidlabile groups.

Additional preferred deblocking resins include at least three distinctrepeating units of 1) units that contain acid-labile groups; 2) unitsthat are free of reactive groups as well as hydroxy groups; and 3)aromatic or other units that contribute to aqueous developability of aphotoresist containing the polymer as a resin binder, Particularlypreferred deblocking polymers of this type correspond to the followingFormula I:

wherein R of units 1) is substituted or unsubstituted alkyl preferablyhaving 1 to about 10 carbon atoms, more typically 1 to about 6 carbons.Branched alkyl such as tert-butyl are generally preferred R groups.Also, the polymer may comprise a mixture of different R groups, e.g., byusing a variety of acrylate monomers during the polymer synthesis.

R¹ groups of units 2) of the above Formula I each independently may bee.g. halogen (particularly F, Cl and Br), substituted or unsubstitutedalkyl preferably having 1 to about 8 carbons, substituted orunsubstituted alkoxy preferably having 1 to about 8 carbon atoms,substituted or unsubstituted alkenyl preferably having 2 to about 8carbon atoms, substituted or unsubstituted alkynyl preferably having 2to about 8 carbons, substituted or unsubstituted alkylthio preferablyhaving 1 to about 8 carbons, cyano, nitro, etc.; and m is an integer offrom 0 (where the phenyl ring is fully hydrogen-substituted) to 5, andpreferably is 0, 1 or 2. Also, two R¹ groups on adjacent carbons may betaken together to form (with ring carbons to which they are attached)one, two or more fused aromatic or alicyclic rings having from 4 toabout 8 ring members per ring. For example, two R¹ groups can be takentogether to form (together with the depicted phenyl) a naphthyl oracenaphthyl ring. As with units 1), the polymer may comprise a mixtureof different units 2) with differing R¹ groups or no R¹ groups (i.e.m=0) by using a variety of substituted or unsubstituted vinylphenylmonomers during the polymer synthesis.

R² groups of units 3) of the above Formula I each independently may bee.g. halogen (particularly F, Cl and Br), substituted or unsubstitutedalkyl preferably having 1 to about 8 carbons, substituted orunsubstituted alkoxy preferably having 1 to about 8 carbon atoms,substituted or unsubstituted alkenyl preferably having 2 to about 8carbon atoms, substituted or unsubstituted sulfonyl preferably having 1about to about 8 carbon atoms such as mesyl (CH₃SO₂O), substituted orunsubstituted alkyl esters such as those represented by RCOO— where R ispreferably an alkyl group preferably having 1 to about 10 carbon atoms,substituted or unsubstituted alkynyl preferably having 2 to about 8carbons, substituted or unsubstituted alkylthio preferably having 1 toabout 8 carbons, cyano, nitro, etc.; and p is an integer of from 0(where the phenyl ring has a single hydroxy substituent) to 4, andpreferably is 0, 1 or 2. Also, two R² groups on adjacent carbons may betaken together to form (with ring carbons to which they are attached)one, two or more fused aromatic or alicyclic rings having from 4 toabout 8 ring members per ring. For example, two R² groups can be takentogether to form (together with the phenol depicted in Formula I) anaphthyl or acenaphthyl ring. As with units 1), the polymer may comprisea mixture of different units 3) with differing R² groups or no R² groups(i.e. p=0) by using a variety of substituted or unsubstitutedvinylphenyl monomers during the polymer synthesis. As shown in Formula Iabove, the hydroxyl group of units 3) may be either at the ortho, metaor para positions throughout the copolymer. Para or meta substitution isgenerally preferred.

Each R³, R⁴ and R⁵ substituent independently may be hydrogen orsubstituted or unsubstituted alkyl preferably having 1 to about 8 carbonatoms, more typically 1 to about 6 carbons, or more preferably 1 toabout 3 carbons.

The above-mentioned substituted groups (i.e. substituted groups R and R¹through R⁵ of Formula I above) may be substituted at one or moreavailable positions by one or more suitable groups such as halogen(particularly F, Cl or Br); C₁₋₈ alkyl; C₁₋₈ alkoxy; C₂₋₈ alkenyl; C₂₋₈alkynyl; aryl such as phenyl; alkanoyl such as a C₁₋₆ alkanoyl of acyland the like; etc. Typically a substituted moiety is substituted at one,two or three available positions.

In the above Formula I, x, y and z are the mole fractions or percents ofunits 3), 2) and 1) respectively in the copolymer. These mole fractionsmay suitably vary over rather wide values, e.g., x may be suitably fromabout 10 to 90 percent, more preferably about 20 to 90 percent; y may besuitably from about 1 to 75 percent, more preferably about 2 to 60percent; and z may be 1 to 75 percent, more preferably about 2 to 60percent.

Preferred copolymers of the above Formula I include those where the onlypolymer units correspond to the general structures of units 1), 2) and3) above and the sum of the mole percents x, y and z equals one hundred.However, preferred polymers also may comprise additional units whereinthe sum of x, y and z would be less than one hundred, althoughpreferably those units 1), 2) and 3) would still constitute a majorportion of the copolymer, e.g. where the sum of x, y and z would be atleast about 50 percent (i.e. at least 50 molar percent of the polymerconsists of units 1), 2) and 3)), more preferably the sum of x, y and zis at least 70 percent, and still more preferably the sum of x, y and zis at least 80 or 90 percent. See European Published Patent ApplicationEP 0813113A1 for detailed disclosure of free radical synthesis ofcopolymers of the above Formula I.

Additional resin binders include those that have acetalester and/orketalester deblocking groups. Such resins are disclosed in EP 0829766A2of the Shipley Company and U. Kumar. For instance, suitable resinsinclude terpolymers formed from hydroxystryene, styrene and acid labilecomponents such as 1-propyloxy-1-ethylmethacrylate and the like.

Additional preferred polymers are disclosed in copending and commonlyassigned U.S. application Ser. No. 09/143,462, filed on Aug. 28, 1998,now U.S. Pat. No. 6,136,501.

Polymers of the invention can be prepared by a variety of methods. Onesuitable method is free radical polymerization, e.g., by reaction ofselected monomers to provide the various units as discussed above in thepresence of a radical initiator under an inert atmosphere (e.g., N₂ orargon) and at elevated temperatures such as about 70° C. or greater,although reaction temperatures may vary depending on the reactivity ofthe particular reagents employed and the boiling point of the reactionsolvent (if a solvent is employed). Suitable reaction solvents includee.g. tetrahydrofuran, dimethylformamide and the like. Suitable reactiontemperatures for any particular system can be readily determinedempirically by those skilled in the art based on the present disclosure.Monomers that can be reacted to provide a polymer of the invention canbe readily identified by those skilled in the art based on the presentdisclosure. For example, suitable monomers include e.g. acrylate,including methacrylate, t-butylacrylate, acrylonitrile,methacrylonitrile, itaconic anhydride and the like. A variety of freeradical initiators may be employed to prepare the copolymers of theinvention. For example, azo compounds may be employed such asazo-bis-2,4-dimethylpentanenitrile. Peroxides, peresters, peracids andpersulfates also could be employed.

Unless indicated otherwise above, a polymer used as a resin bindercomponent of a resist of the invention typically will have a weightaverage molecular weight (M_(w)) of 1,000 to about 100,000, morepreferably about 2,000 to about 30,000, still more preferably from about2,000 to 15,000 or 20,000, with a molecular weight distribution(M_(w)/M_(n)) of about 3 or less, more preferably a molecular weightdistribution of about 2 or less. Molecular weights (either M_(w) orM_(n)) of the polymers of the invention are suitably determined by gelpermeation chromatography.

Preferred polymers also will exhibit a sufficiently high T_(g) tofacilitate use of the polymer in a photoresist. Thus, preferably apolymer will have a T_(g) greater than typical softbake (solventremoval) temperatures, e.g. a T_(g) of greater than about 100° C., morepreferably a T_(g) of greater than about 110° C., still more preferablya T_(g) of greater than about 120° C.

For 193 nm imaging applications, preferably a resist resin bindercomponent will be substantially free of any phenyl or other aromaticgroups. For example, preferred polymers for use in 193 imaging containless than about 1 mole percent aromatic groups, more preferably lessthan about 0.1, 0.02, 0.04 and 0.08 mole percent aromatic groups andstill more preferably less than about 0.01 mole percent aromatic groups.Particularly preferred polymers are completely free of aromatic groups.Aromatic groups can be highly absorbing of sub-200 nm radiation and thusare undesirable for polymers used in photoresists imaged 193 nm.

Photoresists of the invention also may contain other materials. Forexample, other optional additives include actinic and contrast dyes,anti-striation agents, plasticizers, speed enhancers, etc. Such optionaladditives typically will be present in minor concentration in aphotoresist composition except for fillers and dyes which may be presentin relatively large concentrations such as, e.g., in amounts of from 5to 30 percent by weight of the total weight of a resist's drycomponents. A preferred additive is a basic compound, such astetrabutylammonium hydroxide (TBAH), tetrabutylammonium lactate, ortetrabutylammonium acetate, which can enhance resolution of a developedimage. For resists imaged at 193 nm, a preferred added base is ahindered amine such as diazabicycloundecene, diazabicyclononene ordi-terbutylethanolamine. Such an amine may be suitably present in amountof about 0.03 to 5 to 10 weight percent, based on total solids (allcomponents except solvent) of a resist composition.

The PAG blend component should be present in a photoresist formulationin amount sufficient to enable generation of a latent image in a coatinglayer of the resist. More specifically, the PAG blend will suitably bepresent in an amount of from about 0.5 to 40 weight percent of totalsolids of a resist, more typically from about 0.5 to 10 weight percentof total solids of a resist composition. The distinct PAGs of a blendsuitably may be present in about equivalent molar amounts in a resistcomposition, or each PAG may be present in differing molar amounts. Itis typically preferred however that each class or type of PAG is presentin an amount of at least about 20 to 25 mole percent of total PAGpresent in a resist formulation.

The resin binder component of resists of the invention are typicallyused in an amount sufficient to render an exposed coating layer of theresist developable such as with an aqueous alkaline solution. Moreparticularly, a resin binder will suitably comprise 50 to about 90weight percent of total solids of the resist.

The photoresists of the invention are generally prepared following knownprocedures with the exception that a photoactive component of theinvention is substituted for prior photoactive compounds used in theformulation of such photoresists. For example, a resist of the inventioncan be prepared as a coating composition by dissolving the components ofthe photoresist in a suitable solvent such as, e.g., a glycol ether suchas 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl ether,propylene glycol monomethyl ether, propylene glycol monomethyl etheracetate; lactates such as ethyl lactate or methyl lactate, with ethyllactate being preferred; proponiates, particularly methyl propionate,ethyl propionate and ethyl ethoxy propionate; a Cellosolve ester such asmethyl Cellosolve acetate; an aromatic hydrocarbon such toluene orxylene; a ketone such as methylethyl ketone or cyclohexanone; and thelike. Typically the solids content of the photoresist varies between 5and 35 percent by weight of the total weight of the photoresistcomposition.

The photoresists of the invention can be used in accordance with knownprocedures. Though the photoresists of the invention may be applied as adry film, they are preferably applied on a substrate as a liquid coatingcomposition, dried by heating to remove solvent preferably until thecoating layer is tack free, exposed through a photomask to activatingradiation, optionally post-exposure baked to create or enhancesolubility differences between exposed and nonexposed regions of theresist coating layer, and then developed preferably with an aqueousalkaline developer to form a relief image.

The substrate suitably can be any substrate used in processes involvingphotoresists such as a microelectronic wafer. For example, the substratecan be a silicon, silicon dioxide or aluminum-aluminum oxidemicroelectronic wafer. Gallium arsenide, ceramic, quartz or coppersubstrates may also be employed. Substrates used for liquid crystaldisplay and other flat panel display applications are also suitablyemployed, e.g. glass substrates, indium tin oxide coated substrates andthe like. As discussed above, it has been found that highly resolvedresist relief images can be formed on substrates that can be difficultto pattern fine images, such as boron phosphorus silicate glass. Aliquid coating resist composition may be applied by any standard meanssuch as spinning, dipping or roller coating.

Also, rather than applying a resist composition directly onto asubstrate surface, a coating layer of an antireflective coatingcomposition may be first applied onto a substrate surface and thephotoresist coating layer applied over the underlying antireflectivecoating. A number of antireflective coating compositions may be employedincluding the compositions disclosed in European ApplicationsPublication Nos. 0542008A1 and 0813114A2, both of the Shipley Company.For resists to be imaged at 248 nm, an antireflective composition thatcontains a resin binder with anthracene units preferably may beemployed.

The exposure energy should be sufficient to effectively activate thephotoactive component of the radiation sensitive system to produce apatterned image in the resist coating layer. Suitable exposure energiestypically range from about 10 to 300 mJ/cm². An exposure wavelength inthe deep U.V. range often preferably will be used for the photoresistsof the invention, particularly exposure wavelengths of sub-250 nm orsub-200 nm such as about 248 nm or 193 nm. Preferably, the exposedresist coating layer will be thermally treated after exposure and priorto development, with suitable post-exposure bake temperatures being fromabout e.g. 50° C. or greater, more specifically from about 50 to 160° C.After development, the substrate surface bared by development may thenbe selectively processed, for example chemically etching or platingsubstrate areas bared of photoresist in accordance with procedures knownin the art. Suitable etchants include a hydrofluoric acid etchingsolution and a plasma gas etch such as an oxygen plasma etch.

All documents mentioned herein are incorporated herein by reference. Thefollowing non-limiting examples are illustrative of the invention.

EXAMPLE 1

Resist preparation (comparative resists and resist of the invention)

Three photoresist compositions were prepared and are referred herein asResists 1, 2 and 3 respectively. Each of Resists 1, 2 and 3 had thefollowing same components: 1) terpolymer resin having polymerized unitsof hydroxystyrene, styrene and tert-butyl acrylate; 2) additives oftetrabutylammonium hydroxide (0.3 wt. % of terpolymer), acalixresorcinarene (3 wt. % of terpolymer), and surfactant (Silwet L7604at 0.5 wt. % of total solids). Resist 1 (comparative) contained a singlePAG of di-(4-t-butylphenyl)iodonium camphorsulfonate PAG (5 wt. % ofpolymer). Resist 2 contained a PAG blend that consisted of the twocompounds of di-(4-t-butylphenyl)iodonium camphorsulfonate PAG (at 2.5wt. % of polymer) and di-(4-t-butylphenyl)iodoniumo-trifluoromethylbenzenesulfonate PAG (at 2.5 wt. % of polymer). Resist3 (comparative) contained a single PAG of di-(4-t-butylphenyl)iodoniumo-trifluoromethylbenzenesulfonate PAG (at 5 wt. % of polymer).

Each of Resists 1, 2 and 3 were prepared at 16 wt. % solids with asolvent of ethyl lactate, rolled to dissolve, and then filtered to 0.2μm,

EXAMPLE 2

Lithographic results

The lithographic evaluation of these resists was performed and analyzedas follows.

Resists 1, 2 and 3 were at room temperature and coated over an organicantireflective composition coating that had been coated onto unprimedsilicon wafers and baked at 225° C. for 60 seconds, yielding a 600angstrom film of the antireflective composition coating layer. Resists1, 2 and 3 were coated to provide approximately 6000 angstrom resistcoating after a softbake of 130° C. for 60 seconds. Eo photospeed wasdetermined by exposing a coated wafer of each resist with a 0.1-10.0mJ/cm² dose range using an open-field mask on a GCA XLS7800 Deep UVStepper (248.4 nm krypton fluoride laser, 0.53 numerical aperture, 0.74partial coherence). Each exposed film was post-exposure baked at 130°for 90 seconds and then developed with Ad-10 (2.38% TMAH) developer for40 seconds in double puddle mode (20/20 sec. process). The EOphotospeeds of Resists 1, 2 and 3 were 4.3, 3.8, and 3.3 mJ/cm²,respectively. The resists were then tested for imaging performance byproducing dense and isolated contact hole features over an exposurerange beginning at 3×EO, incrementing at 0.1×EO (for 16 steps), andending at approximately 4.6×EO, and over a focus range of 1.8 μm,centered at the machine-determined 0 focus, with 0.15 urn increments.The imaged wafers were analyzed for exposure latitude (EL) for 0.25 μm1:1 contact holes via scanning electron microscopy (SEM). Results areset forth in Table 1 immediately below.

TABLE 1 (Energies in mJ/cm²) E0.20 Sample Eo E0.22 (Esize) E0.18 ELEs/E0 Resist 1 4.3 15.96 15.03 14.10 12.4% 3.50 Resist 2 3.8 14.58 13.6012.61 14.5% 3.58 Resist 3 3.3 13.00 12.49 11.98  8.2% 3.79

2. Focus latitude.

Focus latitude analysis was performed over the 0.2 μm target CD of thecontact holes for each of Resists 1, 2 and 3. Results are set forth inTable 2 immediately below.

TABLE 2 Focus Latitude Sample 0.25 um Contact Holes Resist 1 0.35 umResist 2 0.75 um Resist 3 0.5 um 

As can be seen from Tables 1 and 2, Resist 2, which contained a PAGblend of the invention showed the highest exposure latitude and focuslatitude. Hence, that resist of the invention offers an improvedlithographic process window.

EXAMPLE 3

Additional lithographic results

Two photoresists were prepared and are referred to herein as Resists 4and 5. Each of Resists 4 and 5 had the following same components: 1)terpolymer resin having polymerized units of hydroxystyrene, styrene andtert-butyl acrylate; 2) additives of tetrabutylammonium hydroxide (0.125wt. % of terpolymer), and surfactant (Fluorad FC-430 at 0.1 wt. % oftotal solids). Resist 4 (comparative) contained a single PAG ofdi-(4-t-butylphenyl)iodonium o-trifluoromethylbenzenesulfonate PAG (2wt. % of polymer). Resist 5 contained a PAG blend that consisted of thetwo compounds of di-(4-t-butylphenyl)iodonium camphorsulfonate PAG (0.76wt. % of polymer) and di-(4-t-butylphenyl)iodoniumo-trifluoromethylbenzenesulfonate PAG (1.25 wt. % of polymer).

Each of Resists 4 and 5 were prepared at 16 wt. % solids with a solventof ethyl lactate, rolled to dissolve, and then filtered to 0.2 μm.

Resist 4 and 5 were each coated, soft-baked, imaged to 248 nm radiation,post-exposure baked and developed as described in Example 2 above. TheResists 4 and 5 were exposed to provide for both 0.25 μm and 0.20 μmline/space (l/s) pairs and isolated lines (Iso). Exposure latituderesults are set forth in Table 3 below.

TABLE 3 Sample 1:1 0.25 μm l/s Iso 0.25 μm 1:1 0.20 μm l/s Iso 0.20 μmResist 4  7.9% 10.5% 2.7% 2.2% Resist 5 14.1% 13.0% 8.3% 8.7   

As can be seen from the results in Table 3 above, Resist 5 (containing aPAG blend of the invention) showed significantly improved exposurelatitude relative to Resist 4, particularly for smaller features whereextension of the process window (e.g. exposure latitude) can becritical. In addition, Resist 5 showed significantly higher qualityrelief image profiles relative to Resist 4.

EXAMPLE 4

Boron Phosphorus Silicate Glass Substrate Application

Three photoresist compositions were prepared and are referred to hereinas Resists 6, 7 and 8. Each of Resists 6, 7, 8 contained a copolymerresin that 65 mole percent hydroxystyrene units and 35 mole percent oftert-butyl acrylate units; tetrabutylammonium hydroxide at 0.4 wt. %relative to polymer weight; Silwet L7604 at 0.4 weight % relative tototal solids. Resist 6 contained a PAG ofdi-(4-tert-butylphenyl)iodonium camphorsulfonate at 5 weight % relativeto the resin. Resist 7 contained a PAG blend that consisted of 2.5weight % relative to the resin of di-(4-tert-butylphenyl)iodoniumcamphorsulfonate and 2.5 weight % relative to the resin ofdi-(4-tert-butylphenyl)iodonium perfluoroctanesulfonate. Resist 8contained a PAG blend that consisted of 1 weight % relative to the resinof di-(4-tert-butylphenyl)iodonium camphorsulfonate and 4 weight %relative to the resin of di-(4-tert-butylphenyl)iodoniumperfluoroctanesulfonate.

Each of Resists 6, 7 and 8 were prepared at 16 wt. % solids with asolvent of ethyl lactate, rolled to dissolve, and then filtered to 0.2μm, and then coated onto boron phosphorus silicate glass substrates andbaked at 130° C. for 60 seconds, exposed at 248 nm, 150° C./90 secondpost-exposure bake and 30 second/30 second double puddle alkalineaqueous solution development. Resists 7 and 8 provided fasterphotospeeds (relative to Resist 6), no footing of the developed 0.25 μmcontact hole relief image and greatly reduced standing waves on boronphosphorus silicate glass substrates. The relief image of comparativeResist 6 showed significant footing and severe standing waves.

The foregoing description of the invention is merely illustrativethereof, and it is understood that variations and modifications can beeffected without departing from the spirit or scope of the invention asset forth in the following claims.

What is claimed is:
 1. A photoresist composition comprising: a resinbinder an a mixture of photoacid generator compounds in an amountsufficient to permit development of an exposed coating layer of thecomposition, the photoacid generator compound mixture comprising a firstphotoacid generator onium compound and a second photoacid generatoronium compound, wherein the first and second photoacid generatorsgenerate a first photoacid and a second photoacid respectively uponphotoactivation that differ in pKa values by at least about 0.5, and thesecond photoacid has a pKa of about 0 or greater.
 2. The photoresistcomposition of claim 1 wherein the first and second photoacid generatorsgenerate acids upon photoactivation that differ in pKa values by atleast about
 1. 3. The photoresist composition of claim 1 wherein thefirst and second photoacid generators generate acids uponphotoactivation that differ in pKa values by at least about 1.5.
 4. Thephotoresist composition of claim 1 wherein the first photoacid has a pKaof about −1 or less.
 5. The photoresist composition of claim 1 whereinthe first photoacid has a pKa of about −2 or less.
 6. The photoresistcomposition of claim 5 wherein the second photoacid generator has a pKaof about 0 or greater.
 7. The photoresist of claim 1 wherein thephotoacid generated by first or second photoacid generator is aperfluoroalkyl sulfonic acid.
 8. The photoresist of claim 1 wherein thefirst and second photoacids differ in size by at least about 40 Å³. 9.The photoresist composition of claim 1 wherein both the first photoacidgenerator compound and second photoacid generator compound are iodoniumcompounds.
 10. The photoresist composition of claim 9 wherein the firstor second photoacids is a perfluorinated alkylsulfonic acid.
 11. Thephotoresist composition of claim 9 wherein the first or secondphotoacids is a perfluorooctanesulfonic acid, a perfluorohexanesulfonicacid, a perfluorbutanesulfonic acid, or a trifluoromethanesulfonic acid.12. The photoresist composition of claim 1 wherein both the firstphotoacid generator compound and second photoacid generator compound aresulfonium compounds.
 13. The photoresist composition of claim 1 whereinone of the first photoacid generator compound and the second photoacidgenerator compound is a sulfonium compound, and the other is an iodoniumcompound.
 14. The photoresist composition of claim 1 wherein the firstor second photoacids is a perfluorinated alkylsulfonic acid.
 15. Thephotoresist composition of claim 1 wherein the first or secondphotoacids is a perfluorooctanesulfonic acid, a perfluorohexanesulfonicacid, a perfluorobutanesulfonic acid, or a trifluoromethanesulfonicacid.
 16. The photoresist composition of claim 1 wherein the first orsecond photoacids is a cycloalkylsulfonic acid.
 17. The photoresistcomposition of claim 1 wherein the first or second photoacids is acyclohexane sulfonic acid, an adamanatanesulfonic acid or a camphorsulfonic acid.
 18. A photoresist composition comprising: a resin binderan a mixture of photoacid generator compounds in an amount sufficient topermit development of an exposed coating layer of the composition, thephotoacid generator compound mixture comprising a first photoacidgenerator onium compound and a second photoacid generator oniumcompound, wherein the first and second photoacid generators generate afirst photoacid and a second photoacid respectively upon photoactivationthat differ in size by at least about 40 Å³, and the second photoacidhas a pKa of about 0 or greater.
 19. The photoresist of claim 18 whereinthe first and second photoacid generators generate acids uponphotoactivation that differ in size by at least about 50 Å³.
 20. Thephotoresist composition of claim 18 wherein the first photoacid has avolume of at least about 150 Å³.
 21. The photoresist composition ofclaim 18 wherein both the first photoacid generator compound and secondphotoacid generator compound are iodonium compounds.
 22. The photoresistcomposition of claim 18 wherein both the first photoacid generatorcompound and second photoacid generator compound are sulfoniumcompounds.
 23. The photoresist composition of claim 18 wherein one ofthe first photoacid generator compound and the second photoacidgenerator compound is a sulfonium compound, and the other is an iodoniumcompound.
 24. A method for forming a photoresist relief image on asubstrate comprising: (a) applying a coating layer of a photoresistcomposition of claim 1 on a substrate; and (b) exposing the photoresistcoating layer to patterned activating radiation and developing theexposed photoresist layer to provide a relief image.
 25. A method forforming a photoresist relief image on a substrate comprising: (a)applying a coating layer of a photoresist composition of claim 18 on asubstrate; and (b) exposing the photoresist coating layer to patternedactivating radiation and developing the exposed photoresist layer toprovide a relief image.
 26. An article of manufacture comprising asubstrate having on at least one surface a coating layer of thephotoresist composition of claim
 1. 27. An article of manufacturecomprising a substrate having on at least one surface a coating layer ofthe photoresist composition of claim
 18. 28. The article of claim 27wherein the substrate is a microelectronic wafer substrate or a flatpanel display substrate.
 29. A photoacid generator compound mixturecomprising a first photoacid generator onium compound and a secondphotoacid generator onium compound, wherein the first and secondphotoacid generators generate a first photoacid and a second photoacidrespectively upon photoactivation that differ in pKa values by at leastabout 0.5, and the second photoacid has a pKa of about 0 or greater. 30.The photoacid generator mixture of claim 29 wherein the first and secondphotoacids differ in size by at least about 40 Å³.
 31. A photoacidgenerator compound mixture comprising a first photoacid generator oniumcompound and a second photoacid generator onium compound, wherein thefirst and second photoacid generators generate a first photoacid and asecond photoacid respectively upon photoactivation that differ in sizeby at least about 40 Å³, and the second photoacid has a pKa of about 0or greater.
 32. A photoresist composition comprising: a resin binder anda mixure of photoacid generator compounds in an amount sufficient topermit development of an exposed coating layer of the composition, thephotoacid generator compound mixture comprising a first photoacidgenerator diazosulfonyl compound and a second photoacid generator thatis a diazosulfonyl compound, wherein the first and second photoacidgenerator compounds generate a first photoacid and a second photoacidrespectively upon photoactivation that differ in pKa values by at leastabout 0.5 and differ in size by at least about 40 cubic angstroms. 33.The photoresist composition of claim 32 wherein the first and secondphotoacid generators generate acids upon photoactivation that differ inpKa values by at least about
 1. 34. The photoresist composition of claim32 wherein the first photoacid has a pKa of about −1 or less.
 35. Thephotoresist composition of claim 32 wherein the photoresist comprises aresin that contains phenolic and alkyl acrylate units.
 36. Thephotoresist composition of claim 32 wherein the photoresist comprises aresin that contains alkyl acrylate units and is essentially free ofphenyl or other aromatic units.
 37. A photoresist compositioncomprising: a) a resin binder that is a copolymer that contain phenoland alkyl acrylate units; b) a mixture of photoacid generator compoundsin an amount sufficient to permit development of an exposed coatinglayer of the composition, the photoacid generator compound mixturecomprising a first photoacid generator diazosulfonyl compound and asecond photoacid generator that is a diazosulfonyl compound, wherein thefirst and second photoacids generate a first photoacid and a secondphotoacid respectively upon photoactivation that differ in size by atleast about 40 cubic angstroms.
 38. The photoresist composition of claim37 wherein the first and second photoacid generators generate acids uponphotoactivation that differ in size by at least about 50 cubicangstroms.
 39. The photoresist composition of claim 37 wherein thephotoresist comprises a resin that contains phenolic and alkyl acrylateunits.
 40. The photoresist composition of claim 37 wherein thephotoresist comprises a resin that contains alkyl acrylate units and isessentially free of phenyl or other aromatic units.
 41. A photoresistcomposition comprising: a resin binder and a mixure of photoacidgenerator compounds in an amount sufficient to permit development of anexposed coating layer of the composition, the photoacid generatorcompound mixture comprising a first photoacid generator that is an oniumsalt and a second photoacid generator that is an imidosulfonatecompound, a N-sulfonyloxyimide compound, a diazosulfonyl compound, anitrobenzyl compound, a sulfone compound, or a halogenated, non-ionicphotoacid generating compound, wherein the first and second photoacidgenerator compounds generate a first photoacid and a second photoacidrespectively upon photoactivation that differ in pKa values by at leastabout 0.5 and differ in size by at least about 40 cubic angstroms; andthe resin binder comprises a resin selected from the group consistingof: i) a resin that contains phenolic and alkyl acrylate units, and ii)a resin that contains alkyl acrylate units and is essentially free ofphenyl or other aromatic units.
 42. The photoresist composition of claim41 wherein the first and second photoacid generators generate acids uponphotoactivation that differ in pKa values by at least about
 1. 43. Thephotoresist composition of claim 41 wherein the first photoacid has apKa of about −1 or less.
 44. A photoresist composition comprising: a) aresin that contains phenolic and alkyl acrylate units; b) a mixture ofphotoacid generator compounds in an amount sufficient to permitdevelopment of an exposed coating layer of the composition, thephotoacid generator compound mixture comprising a first photoacidgenerator that is an onium compound and a second photoacid generatorthat is an imidosulfonate compound, a N-sulfonyloxyimide compound, adiazosulfonyl compound, a nitrobenzyl compound, a sulfone compound, or ahalogenated, non-ionic photoacid generating compound, wherein the firstand second photoacids generate a first photoacid and a second photoacidrespectively upon photoactivation that differ in size by at least about40 cubic angstroms.
 45. The photoresist composition of claim 44 whereinthe first and second photoacid generators generate acids uponphotoactivation that differ in size by at least about 50 cubicangstroms.
 46. The photoresist composition of claim 44 wherein thephotoresist comprises a resin that contains phenolic and alkyl acrylateunits.
 47. The photoresist composition of claim 44 wherein thephotoresist comprises a resin that contains alkyl acrylate units and isessentially free of phenyl or other aromatic units.
 48. A photoresistcomposition comprising: a resin binder an a mixture of photoacidgenerator compounds in an amount sufficient to permit development of anexposed coating layer of the composition, the photoacid generatorcompound mixture comprising a first photoacid generator compound and asecond photoacid generator compound that are each independently selectedfrom the group consisting of an imidosulfonate compound, aN-sulfonyloxyimide compound, a diazosulfonyl compound, a nitrobenzylcompound, a sulfone compound, and a halogenated, non-ionic photoacidgenerating compound, wherein the first and second photoacid generatorsgenerate a first photoacid and a second photoacid respectively uponphotoactivation that differ in pKa values by at least about 0.5; and theresin binder comprises a resin selected from the group consisting of: i)a resin that contains phenolic and alkyl acrylate units and ii) a resinthat contains alkyl acrylate units and is essentially free of phenyl orother aromatic units.
 49. The photoresist composition of claim 48wherein the first and second photoacid generators generate acids uponphotoactivation that differ in pKa values by at least about
 1. 50. Thephotoresist composition of claim 48 wherein the first photoacid has apKa of about −1 or less.
 51. The photoresist composition of claim 48wherein the first and second photoacids differ in size by at least about40 cubic angstroms.
 52. A photoresist composition comprising: a) a resinbinder that is a copolymer that contain phenol and alkyl acrylate units;b) a mixture of photoacid generator compounds in an amount sufficient topermit development of an exposed coating layer of the composition, thephotoacid generator compound mixture the photoacid generator compoundmixture comprising a first photoacid generator compound and a secondphotoacid generator compound that are each independently selected fromthe group consisting of an imidosulfonate compound, a N-sulfonyloxyimidecompound, a diazosulfonyl compound, a nitrobenzyl compound, a sulfonecompound, and a halogenated, non-ionic photoacid generating compound,wherein the first and second photoacids generate a first photoacid and asecond photoacid respectively upon photoactivation that differ in sizeby at least about 40 cubic angstroms.
 53. The photoresist composition ofclaim 52 wherein the first and second photoacid generators generateacids upon photoactivation that differ in size by at least about 50cubic angstroms.
 54. A photoresist of claim 52 wherein the copolymer hasrepeating units x and y of the following formula:

R′ is substituted or unsubstituted alkyl having 1 to about 18 carbonatoms.
 55. A photoresist of claim 52 wherein the copolymer has ret tingunits x, y and z of the following formula:

R is substituted or unsubstituted alkyl; R¹ and R² are independentlysubstituted or unsubstituted alkyl; substituted or unsubstituted alkoxy;substituted or unsubstituted alkenyl; substituted or unsubstitutedalkynyl; substituted or unsubstituted alkylthio; cyano; or nitro; R³, R⁴and R⁵ are independently hydrogen or substituted or unsubstituted alkyl;m is an integer of from 0 to 5; and p is an integer of from 0 to
 4. 56.A positive photoresist composition comprising: a) a resin containsphenolic and alkyl acrylate units; b) a mixture of photoacid generatorcompounds in an amount sufficient to permit development of an exposedcoating layer of the composition, the photoacid generator compoundmixture comprising a first photoacid generator compound and a secondphotoacid generator compound, wherein the first and second photoacidsgenerate a first photoacid and a second photoacid respectively uponphotoactivation that differ in pKa values by at least about 0.5.
 57. Thephotoresist composition of claim 56 wherein the first and secondphotoacid generators generate acids upon photoactivation that differ inpKa values by at least about
 1. 58. The photoresist composition of claim57 wherein the first or second photoacid generators is an oniumcompound.
 59. The photoresist composition of claim 57 wherein the firstor second photoacid generators is an iodonium compound.
 60. Thephotoresist composition of claim 57 wherein both the first and secondphotoacid generators are iodonium compounds.
 61. The photoresistcomposition of claim 57 wherein the first or second photoacids is aperfluorinated alkylsulfonic acid.
 62. The photoresist composition ofclaim 61 wherein the first ory second photoacids is a cycloalkylsulfonicacid.
 63. The photoresist composition of claim 61 wherein the first orsecond photoacids is a cyclohexane sulfonic acid, an adamanatanesulfonicacid or a camphor sulfonic acid.
 64. The photoresist composition ofclaim 57 wherein the first or second photoacids is aperfluorooctanesulfonic acid, a perfluorohexanesulfonic acid, aperfluorbutanesulfonic acid, or a trifluoromethanesulfonic acid.
 65. Thephotoresist composition of claim 57 wherein the first or secondphotoacids is a cycloalkylsulfonic acid.
 66. The photoresist compositionof claim 57 wherein the first or second photoacids is a cyclohexanesulfonic acid, an adamanatanesulfonic acid or a camphor sulfonic acid.67. The photoresist composition of claim 56 wherein the first photoacidhas a pKa of about −1 or less.
 68. The photoresist composition of claim57 wherein the first and second photoacids differ in size by at leastabout 40 cubic angstroms.
 69. A photoresist of claim 56 wherein thecopolymer has repeating units x and y of the following formula:

R′ is substituted or unsubstituted alkyl having 1 to about 18 carbonatoms.
 70. A photoresist of claim 56 wherein the copolymer has repeatingunits x, y and z of the following formula:

R is substituted or unsubstituted alkyl; R¹ and R² are independentlysubstituted or unsubstituted alkyl; substituted or unsubstituted alkoxy;substituted or unsubstituted alkenyl; substituted or unsubstitutedalkynyl; substituted or unsubstituted alkylthio; cyano; or nitro; R³, R⁴and R⁵ are independently hydrogen or substituted or unsubstituted alkyl;m is an integer of from 0 to 5; and p is an integer of from 0 to
 4. 71.A positive photoresist composition comprising: a) a resin that containsphenolic and alkyl acrylate units; b) a mixture of photoacid generatorcompounds in an amount sufficient to permit development of an exposedcoating layer of the composition, the photoacid generator compoundmixture comprising a first photoacid generator compound and a secondphotoacid generator compound, wherein the first and second photoacidsgenerate a first photoacid and a second photoacid respectively uponphotoactivation that differ in size by at least about 40 cubicangstroms.
 72. The photoresist composition of claim 71 wherein the firstand second photoacid generators generate acids upon photoactivation thatdiffer in size by at least about 50 cubic angstroms.
 73. The photoresistcomposition of claim 72 wherein the first or second photoacid generatorsis an onium compound.
 74. The photoresist composition of claim 72wherein the first or second photoacid generators is an iodoniumcompound.
 75. The photoresist composition of claim 72 wherein both thefirst and second photoacid generators are iodonium compounds.
 76. Thephotoresist composition of claim 72 wherein the first or secondphotoacids is a perfluorinated alkylsulfonic acid.
 77. The photoresistcomposition of claim 76 wherein the first or second photoacids is acycloalkylsulfonic acid.
 78. The photoresist composition of claim 76wherein the first or second photoacids is a cyclohexane sulfonic acid,an adamanatanesulfonic acid or a camphor sulfonic acid.
 79. Thephotoresist composition of claim 72 wherein the first or secondphotoacids is a perfluorooctanesulfonic acid, a perfluorohexanesulfonicacid, a perfluorbutanesulfonic acid, or a trifluoromethanesulfonic acid.80. The photoresist composition of claim 72 wherein the first or secondphotoacids is a cycloalkylsulfonic acid.
 81. The photoresist compositionof claim 72 wherein the first or second photoacids is a cyclohexanesulfonic acid, an adamanatanesulfonic acid or a camphor sulfonic acid.82. A photoresist of claim 71 wherein the copolymer has repeating unitsx and y of the following formula:

R′ is substituted or unsubstituted alkyl having 1 to about 18 carbonatoms.
 83. A photoresist of claim 71 wherein the copolymer has repeatingunits x, y and z of the following formula:

R is substituted or unsubstituted alkyl; R¹ and R² are independentlysubstituted or unsubstituted alkyl; substituted or unsubstituted alkoxy;substituted or unsubstituted alkenyl; substituted or unsubstitutedalkynyl; substituted or unsubstituted alkylthio; cyano; or nitro; R³, R⁴and R⁵ are independently hydrogen or substituted or unsubstituted alkyl;m is an integer of from 0 to 5; and p is an integer of from 0 to
 4. 84.A positive photoresist composition comprising: a) a resin that containsalkyl acrylate units and is essentially free of phenyl or other aromaticunits; b) a mixture of photoacid generator compounds in an amountsufficient to permit development of an exposed coating layer of thecomposition, the photoacid generator compound mixture comprising a firstphotoacid generator compound and a second photoacid generator compound,wherein the first and second photoacids generate a first photoacid and asecond photoacid respectively upon photoactivation that differ in pKavalues by at least about 0.5.
 85. The photoresist composition of claim84 wherein the first and second photoacid generators generate acids uponphotoactivation that differ in pKa values by at least about
 1. 86. Thephotoresist composition of claim 85 wherein the first or secondphotoacid generators is an onium compound.
 87. The photoresistcomposition of claim 85 wherein the first or second photoacid generatorsis an iodonium compound.
 88. The photoresist composition of claim 85wherein both the first and second photoacid generators are iodoniumcompounds.
 89. The photoresist composition of claim 85 wherein the firstor second photoacids is a perfluorinated alkylsulfonic acid.
 90. Thephotoresist composition of claim 89 wherein the first or secondphotoacids is a cycloalkylsulfonic acid.
 91. The photoresist compositionof claim 89 wherein the first or second photoacids is a cyclohexanesulfonic acid, an adamanatanesulfonic acid or a camphor sulfonic acid.92. The photoresist composition of claim 85 wherein the first or secondphotoacids is a perfluorooctanesulfonic acid, a perfluorohexanesulfonicacid, a perfluorbutanesulfonic acid, or a trifluoromethanesulfonic acid.93. The photoresist composition of claim 85 wherein the first or secondphotoacids is a cycloalkylsulfonic acid.
 94. The photoresist compositionof claim 85 wherein the first or second photoacids is a cyclohexanesulfonic acid, an adamanatanesulfonic acid or a camphor sulfonic acid.95. The photoresist composition of claim 84 wherein the first photoacidhas a pKa of about −1 or less.
 96. The photoresist composition of claim84 wherein the first and second photoacids differ in size by at leastabout 40 cubic angstroms.
 97. The photoresist composition of claim 84wherein the resin is completely free of phenyl or other aromatic units.98. A positive photoresist composition comprising: a) a resin thatcontains alkyl acrylate units and is essentially free of phenyl or otheraromatic units; b) a mixture of photoacid generator compounds in anamount sufficient to permit development of an exposed coating layer ofthe composition, the photoacid generator compound mixture comprising afirst photoacid generator compound and a second photoacid generatorcompound, wherein the first and second photoacids generate a firstphotoacid and a second photoacid respectively upon photoactivation thatdiffer in size by at least about 40 cubic angstroms.
 99. The photoresistcomposition of claim 98 wherein the first and second photoacidgenerators generate acids upon photoactivation that differ in size by atleast about 50 cubic angstroms.
 100. The photoresist composition ofclaim 99 wherein the first or second photoacid generators is an oniumcompound.
 101. The photoresist composition of claim 99 wherein the firstor second photoacid generators is an iodonium compound.
 102. Thephotoresist composition of claim 99 wherein both the first and secondphotoacid generators are iodonium compounds.
 103. The photoresistcomposition of claim 99 wherein the first or second photoacids is aperfluorinated alkylsulfonic acid.
 104. The photoresist composition ofclaim 103 wherein the first or second photoacids is a cycloalkylsulfonicacid.
 105. The photoresist composition of claim 103 wherein the first orsecond photoacids is a cyclohexane sulfonic acid, an adamanatanesulfonicacid or a camphor sulfonic acid.
 106. The photoresist composition ofclaim 99 wherein the first or second photoacids is aperfluorooctanesulfonic acid, a perfluorohexanesulfonic acid, aperfluorbutanesulfonic acid, or a trifluoromethanesulfonic acid. 107.The photoresist composition of claim 99 wherein the first or secondphotoacids is a cycloalkylsulfonic acid.
 108. The photoresistcomposition of claim 99 wherein the first or second photoacids is acyclohexane sulfonic acid, an adamanatanesulfonic acid or a camphorsulfonic acid.
 109. The photoresist composition of claim 98 wherein theresin is completely free of phenyl or other aromatic units.